Hi so I am having some overclocking trouble. I have a powercolor hd 7870 gpu. I've looked up settings people set for this card online and every time I try any of them my games always crash and i gotta restart my computer etc... etc... I just want to know why. Like i cant't overclock this thing like at all. I don't want to increase voltage. Any advice? The box of my gpu says it's good with overclocking, however I have yet to see so.